Problem: Suppose the circumference of a circle is ${2\pi}$. What is its area?
Answer: ${c = 2\pi}$ ${K = 1\pi}$ First, find the radius: $r = c/2\pi = {2\pi}/2\pi = {1}$ Now find the area: $K = \pi r^2$, so $K = \pi \cdot {1}^2 = {1\pi}$.